How to Drill Out a Bolt that Is Broken

If you’ve ever done some DIY project that includes bolts, you probably know nothing is worse than when a bolt or a stud breaks. At first glance, you most likely think there is nothing you can do to fix the situation. The busted latch is still inside, and you have no idea how to get it out. Luckily for you, a few people know how to drill out a bolt that is broken. You can become one of them!

Sure thing, sometimes a bolt can come out with some more straightforward method. A hammer and a chisel can do the trick. If this doesn’t work, though, you’ll be forced to drill the fastener out if you want to reach that bolt. 

In an ideal situation, you will be able to remove the bold and to keep the threads intact. Often, however, threads get damaged beyond salvation. If this happens, you’ll have to repair or replace them, which is a whole new task on its own. Still, learning how to drill out a bolt is essential if you want to ensure you can save any risky housing task. Let’s get started.

What Kind of Drill Bits Do I Need?

Not every drill bit is suitable for this task. There are a few things you should consider when choosing the right one. If you don’t have a good drill bit at your home, it is better to go and buy it than mess around with a bit that won’t hold up to the task. A wrong decision can further ruin your DIY project.

First off, you’ll need left-handed drill bits that are sturdy. These bits are threaded in the opposite direction, and the reverse setting may drive in the bit. You’d want to look for some made of high-speed steel. To ensure they can handle the task, opt for bits that have an additional titanium nitride or cobalt coating. Ideally, the drill bit should have 135-degree split points, as they can make the process much more comfortable. If you have a few drill bits that match the description, we suggest choosing the one from a reliable brand. This provides additional security. 

How to Drill Out a Bolt that Is Broken?

There are two reliable methods to drill out a broken bolt. Both can work, and the decision mostly lies on your preferences and the tools you’ve got. We’ll go over both of them, so you can choose which one is better for you personally.

With an Extracting Kit

To drill out a bolt with an extracting kit, you’ll need to center punch the pin close to the center. Go as close as possible, as this can be crucial. Then, mark the center of the bolt with a hammer and a center punch. This will ensure you drill as close to the middle of the bolt as possible, without damaging the threads. Sure, threads may still break, but this lowers the chances significantly.

Then, create a pilot hole in the center of the bolt. Use a left-handed drill bit, as it will prevent the bolt from tightening. Sometimes, this alone will be enough to unscrew the broken bolt. If you are lucky and this happens, the only thing left is to grab the bolt with pliers or channel locks and extract it completely. If not, you’ll have to use the extractor as well.

Make sure you have the drill bits that are the appropriate size. If you have an extracting kit, there should be a manual to let you know what size bit goes with what bolt. If your bit is too big, you can damage the threads. If the bit is too small, it might break. You’d want to avoid both of those scenarios.

Once you’ve found out what bit size you need, you should place it inside the hole you’ve created. Depending on the extractor type, your bit may have a tapered, left-handed bit on the one side, and a T-handle head or a hex head on the opposite one. You should tap the tapered extractor into place using a hammer. After that, you can switch it to a T-handle or a socket.

The more you tighten in the extractor, the more the tapered end will catch. The torque loosens the bolt until you can entirely remove it from the embedded surface. Make sure you take your time with this process. If you go too fast, you may remove the bolt or the surface you are extracting it from. The extractor itself may break, and repairing it is a costly task.

Once everything is done, remove any metal fillings and shavings that may have fallen off during the extracting process. You can use a brush for that, but we recommend using compressed air or magnet.

The Welding Technique

If you don’t have an extracting kit, you can always learn how to drill out a bolt that is broken using a welding technique. This also works well if you have a corroded bolt that can’t come off with an extractor. Like the first method, you should center punch the broken pin, making sure it’s as close to the middle as possible. Mark the middle of the bold, just like we’ve already explained. Next, you should drill a hole in the center of the bolt. This time, you don’t have to worry too much about using left-handed bits, but it can make this process a lot easier.

While the bolt still exposes threading, tighten a hex nut on top of it. Attach it firmly, but try not to allow it to touch the surface the bolt is embedded on. Now, weld the nut and the bolt together. This is tricky if the embedded surface melts quickly, so be fast and precise. 

Now that the nut and the bold are welded together unscrew it with a wrench or a socket. Make sure the metal has completely cooled down before attempting this! Also, you might have to use a lot of force. If the corrosion is too big, try slowly moving the bolt back and forth until it loosens. This should enable you to complete the process.

Bottom Line

Having a broken bolt is annoying, but the damage can be repaired. If you know how to drill out a bolt the right way, you can salvage your project in minutes.

As you have to use drilling and welding tools for these methods, we’d recommend having someone experienced to help you. Both of these tools can cause severe damage if you don’t use them properly. Make sure you are staying safe.

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